If you haven’t heard about Slack yet, you will. In fact, it may have already infiltrated your company and you just don’t know it yet.

For the uninitiated, Slack is a web-based corporate collaboration tool that allows employees to send messages and files to each other, directly or in self-selected groups. Without experiencing it, Slack admittedly sounds like garden-variety instant messaging; the difficulty of quickly summarizing what it’s good at means that converts often have a wooly, evangelical way of talking about it. This video does a pretty good job of outlining the main points, however:

I’m familiar with the various stages of Slack adoption—resistance, curiosity, bafflement, dawning enthusiasm—because we’re living it right now at PROFIT/Canadian Business. I set up an account last February and have gradually coaxed colleagues into it, at first very tentatively. But in the last few weeks, as Slack chatter has seeped into our office conversation, more co-workers have joined, and it’s starting to have a real and positive impact on the way we work together. (One salutary effect so far is that it’s started to stem the tide of internal all-staff emails, and that alone is cause for celebration.)

The reason Slack has taken root in so many companies is partly the ease of setting it up. Any employee with a company email can start an account for free and invite their colleagues. They can also set their Slack groups to accept new signups from anyone using one of their company’s official email accounts.

For example, a Slack group’s founder, say, Alice@companyX.com, can directly invite Bob@companyX.com to join the group. But she can also prop the door open to anyone with an email containing “@companyX.com,” meaning that Charmaine or Dean or Emily are free to set up an account and join the party already in progress, regardless of how they heard about it.

We did a little experiment to see just how far Slack has already penetrated large corporations: we tried logging in to Slack accounts with fake emails for real companies (e.g., fake.name@google.com). This method meant that we couldn’t actually see anyone’s data (although the computer we used eventually got locked out of the login screen). Because the service can offer accounts automatically to people based on their emails, if you know how an organization structures their email addresses, you can see whether people at that company are using Slack.

And they are. Even with a fairly small, arbitrary list of large Canadian and American companies, we found plenty of major corporations where Slack is already in use. We don’t know by exactly which employees and we can’t tell for what purposes or to what extent, but Slack is here. It may already be in use at your company.

This is the kind of thing that makes tech managers everywhere reach for the Aspirin; employees taking IT matters into their own hands is a perennial headache, and I sympathize with that.

Here’s the thing: no one cares. Any employee with some level of inbox frustration and a little bit of initiative—that would be just about everyone—is looking for something better. Something more efficient and pleasant and beautiful and easy-to-use than whatever ancient, bloated and ugly enterprise software they currently suffer.

Slack’s design and structure means they don’t have to ask for permission. I certainly didn’t. Look around your office—we walk among you.